1. Field of the Invention
The present invention relates to a spray gun for atomizing paints, lacquers or similar media that can be supplied to a workpiece by means of an air flow, in which case the spray gun can be actuated by means of a lever mounted in a pivoting arrangement on a sleeve which accommodates an atomiser nozzle and the air flow can be generated by an air turbine assigned to the spray gun.
2. Description of the Prior Art
A spray gun of this type is described in FR 80 145 66. In this embodiment, the electric motor driving the air turbine can be removed together with the air turbine and is arranged in a separate component on the housing of the spray gun perpendicular to the atomizer nozzle of the spray gun, so that the air flow generated by the air turbine has to have its direction changed several times before it emerges from the atomizer nozzle.
This generates significant flow noise as well as flow losses, therefore this spray gun does not provide a reasonable level of efficiency. A further disadvantage is that the drive motor of the air turbine is only provided with inadequate cooling; this is because the only air flowing past the drive motor is the air drawn in by the air turbine and this air flow is not controlled, meaning that sustained operation is often impossible. Also, this spray gun does not provide any counterbalance because the reservoir container for the medium to be processed and the drive motor with air turbine are arranged ahead of the handle, therefore a high tilting torque is generated whilst the medium is being processed and this tilting torque has to be counteracted by the operating personnel. The principal disadvantage, however, is that the level of noise generated by the air turbine spinning at high speed is only inadequately muffled by the component that houses the motor. As a result, this spray gun has not proved effective in practical use.
The purpose of the present invention is therefore to create a spray gun for atomising medium of the aforementioned type that not only has a straightforward design structure and can be easily operated, but in which above all the operating noise does not attain disruptive levels and there are almost no flow losses which would be caused by changes in the direction of the air flow. Furthermore, the components of the spray gun should be distributed in such a way that either no or only slight tilting torques are generated, therefore permitting work over long periods without leading to fatigue.
In accordance with the present invention, this is achieved in a spray gun of the aforementioned type in that the air turbine and its electric drive motor are arranged coaxially or almost coaxially to the atomiser nozzle of the spray gun on the side of a handle opposite to the sleeve that carries the atomiser nozzle so that the air flow from the air turbine can be supplied in or almost in a straight line through the sleeve of the atomiser nozzle and that the air turbine is provided with a muffler.
In this case, it is advantageous for the muffler, the air turbine and its drive motor to be arranged axially one after the other in the flow direction of the air flow and installed in an attachment formed onto or attached to the handle, so that a high counterweight to the reservoir container attached on the opposite side of the sleeve is created. In addition, a cavity should be provided between the muffler and the air turbine by means of which the flow noise is reduced.
Furthermore, it is advantageous for the movement sequence of the lever that actuates the spray gun to be adapted to a switch associated with the drive motor of the air turbine and that can be influenced by the lever in such a way that the drive motor can be switched on before the atomiser nozzle opens and can be switched off after the atomiser nozzle closes. In this way, it is assured that the medium will only be sprayed when sufficient air flow is available for this and no droplets will be formed when the spray gun is switched on and off.
In order to avoid deflections in the air flow within the spray gun and therefore to avoid flow losses, the attachment that accommodates the muffler, the air turbine and its drive motor should be arranged at an angle α from 0° to 60°, in a preferred embodiment approx. 20°, in relation to the longitudinal axis of the sleeve that carries the atomiser nozzle, opposite to the handle.
Furthermore, the drive motor of the air turbine should be equipped with a jacket that is closed in the axial direction and radially supported in the attachment, it being possible for this jacket to be connected to the sleeve with a connection that can, in a preferred embodiment, be separated. The jacket therefore forms a pressure chamber through which the air flow is guided close to the drive motor of the air turbine so the air flow provides effective cooling.
In accordance with a further embodiment, there is provision for installing a protective grille between the drive motor of the air turbine and the sleeve, with the protective grille being supported, in a preferred embodiment, in the jacket and which should be manufactured from a vibration-damping material, with the possibility of mounting the end of the drive motor of the air turbine that faces away from the air turbine in the protective grille. As a result, satisfactory support for the drive motor is assured.
It has also proven to be extremely advantageous to form the attachment and/or the jacket directly onto the handle and, with a separable connection, on the sleeve that carries the atomiser nozzle, for example by means of a bayonet lock, in which case a container cover can be attached to the sleeve and the container cover should be provided with a holding element, for example in the form of a lug, into which it is possible to engage a web projecting from the handle in order to lock the connection between the attachment or the jacket and the sleeve. In this way, it is possible for the drive part of the spray gun to be separated from its components that are used for atomisation and for the air flow to be used for other purposes, e.g. as a jet of air for blowing out workpieces.
It is also advantageous for the end of the handle to run in the same plane as the standing surface of a reservoir container attached to the spray gun and if the end of the handle is formed as a stand foot, so that the spray gun can be securely put down after use. To reduce the operating noise of the air turbine even more, a sound-absorbing insert should also be arranged between the attachment and the jacket of the drive motor.
The muffler used in the spray gun in accordance with the present invention is, in order to achieve effective acoustic insulation of the intake noise of the air turbine, characterized in that the muffler has a spiral-shaped air duct arranged in a cylindrical housing between an air inlet opening and an air outlet opening, this air duct being formed by two thin-walled partition walls that run in a spiral and are arranged at a lateral distance from one another on a base and/or on a cover of the housing that, in a preferred embodiment, is cylindrical in shape and which project at right angles from the housing, these partition walls combining with the base and the cover to enclose a closed cross-sectional area, that the air inlet opening of the air guide duct is worked into the outer wall of the housing and/or the cover, for example in the form of slots, and that the air outlet opening is arranged centrally in the housing in the base of the housing.
In this case, it is advantageous for the air guide duct to consist of two or more sections running in an almost mirror image arrangement to one another and, in a preferred embodiment, with point symmetry so that the air supply can be evenly distributed over 360°.
Furthermore, it is advantageous for the air guide duct or the two sections that form the air guide duct to be provided with a guide surface in the area of the air outlet opening, the guide surface being spatially curved, and in the case that the air guide duct is composed of two or more sections then the individual sections in the area of the air outlet opening are to be separated from one another by wall sections extending in the axial direction of the air guide duct.
Furthermore it is advantageous for the cross-sectional area of the air guide duct or the sections that form it to be always consistent along its length, in which case if the base and/or the cover of the housing are configured with a funnel shape then the distance between the two partition walls enclosing the air guide duct or enclosing the sections forming the air guide duct is continuously changed in such a way that the enclosed cross-sectional area of the air guide duct is kept constant at all times.
In particular in a housing with a tapered base, the air outlet opening should be followed by an air distributor in the form of a guide body with a tapered configuration.
The housing and/or the cover and the partition walls formed onto them should be configured as an injection-moulded plastic part, in which case it is advantageous for the housing and/or the cover and/or the partition walls formed onto them to be manufactured from a plastic which absorbs or reflects sound, in a preferred embodiment from a plastic incorporating air bubbles and/or pores and, furthermore for the housing and/or the cover and/or the partition walls to be provided with a coating which absorbs and/or reflects sound.
If the partition walls that form the air guide duct are formed onto the base of the housing then it is advantageous for a preferably rubber-like seal to be inserted between them and the cover, the seal corresponding approximately to the inner jacket surface, or for the seal to be attached to the cover.
In order to reduce the noise additionally, it is advantageous for one or more air inlet openings to be provided, e.g. in the form of slots, in the attachment of the spray gun, with the air inlet openings being arranged in a preferred embodiment offset at 90° or 180° in the circumferential direction and/or axially displaced in relation to the air inlet openings worked into the housing and/or the cover of the muffler.
The muffler embodied in accordance with the present invention can form the end air connection of the air turbine and be arranged directly in its intake area.
In a spray gun is embodied in accordance with the present invention, it is possible to atomise a medium with the help of a high-volume air jet without thereby giving rise to unpleasant noise or impeding the handling of the spray gun. The air flow is namely guided almost in a straight line through the attachment accommodating the air turbine as well as the sleeve that carries the atomiser nozzle, there are no deflections in the air flow and the flow resistance values are also minor.
Furthermore, it is advantageous that the arrangement of the sleeve with the atomiser nozzle and the reservoir container on one side of the handle and of the attachment accommodating the air turbine and the drive motor on the other side of the handle provides for an almost even distribution of weight. It is therefore possible to work with the spray gun configured in accordance with the present invention for long periods without uneven loadings leading to fatigue. Also, in particular in the separable embodiment of the spray gun, the spray gun can be used for many different applications by connecting a hose with an air nozzle, for example, to the air turbine in order to be able to perform cleaning work.
The muffler assigned to the air turbine furthermore permits a very effective insulation of the intake noise of the air turbine, since the sucked-in air flow is if necessary divided into several individual flows, sucked in over a long distance and only deflected to a minimum extent in this case. The resistance opposing the sucked-in air is only minor in this case, therefore the air flow rate through the muffler is only impeded to a slight extent.
The thin-walled partition walls forming the air guide duct furthermore only take up a minor proportion of the interior of the housing, so that almost the entirety of the housing can be used for the air flow. Also, the partition walls formed onto the base and/or the cover and contacting the opposite part ensure a high level of stability, by means of which the noise is further reduced. When the muffler in accordance with the present invention is used, it is therefore possible significantly to reduce the environmental impact resulting from the use of the high speed air turbines which generate loud noise.